Because the direct current voltages used in devices inside the electronic equipment, such as television, display, audio, computer, etc., may be different, the input direct current voltage of an electronic equipment is converted to different output voltages for usage of different devices inside the electronic equipment.
Nowadays, a fixed voltage output mode is usually applied for converting the input direct current voltage into output voltage in order to satisfy the usage of specific internal device of the electronic equipment. The drawback is: when the internal device connected to the output voltage is changed and the output voltage for the current internal device is greatly away from the output voltage for the previous internal device such that the voltage output mode cannot satisfy the usage requirement of the current internal device, it is necessary to re-design a voltage output converting mode and therefore the design cost and design period are increased.